Orthodontic treatment requires the use of appliances such as brackets, arch wires, retainers, braces and other paraphernalia in the mouth. When present in the mouth, these appliances interfere with normal oral hygiene. As a result, the prevention and treatment of oral diseases, such as gingivitis, periodontitis and dental caries, becomes very difficult during a course of orthodontic treatment. The appliances provide locations where food can accumulate and they thereby constitute a source for bacteria growth. Accordingly, it would be desirable to make these types of appliances in a manner such as to prevent the adverse effects of bacterial action.
Various efforts have been made to provide antimicrobial action for medical type products to be implanted into the body has been considered. For example, U.S. Pat. No. 5,906,466 describes an antimicrobial composition comprising antimicrobial silver compounds deposited on a physiologically inert oxide support material. In Japanese Patent Abstract No. 08041611 an alloy exhibiting antimicrobial properties is disclosed. None of these are specifically directed to orthodontic appliances.
Attempts have been made to solve various aspects of this problem in the field of orthodontic appliances. For example, in U.S. Pat. No. 5,068,107 an elastic retainer member, such as formed by an elastic polymeric material, is provided with a dentally active pharmacological agent, such as halide salt and various compositions that contain fluoride. The agent is released in the mouth. Such a product suffers from the defect of the agent being depleted over time, thereby requiring replacement of the appliance. Also, this approach is not easily used for metal orthodontic appliances. U.S. Pat. No. 5,716,208 discloses an orthodontic bracket to be attached to a tooth that has an outer coating that contains an organic antimicrobial agent, the preferred one disclosed being 2,4,4'-trichloro-2'-hydroxy-diphenyl ether (triclosan) which is a halogenated diphenyl ether. Triclosan is an organic compound, and therefore suffers from the disadvantage that antibiotic resistance can develop over time with continued use. Furthermore, triclosan is suspected of inducing skin irritation.